Guidance system using changeable signs

ABSTRACT

A guidance system for guiding a user to selected targets located within a defined area, such as a warehouse, museum, parking garage, etc., includes a portable unit to be carried by each user and having a memory for storing target information identifying a selected target within the defined area, and a transmitter for transmitting signals identifying the selected target within the defined area. The system further includes at least one changeable guidance sign at a predetermined location within the defined area for receiving signals transmitted by a portable unit and for displaying stored guidance information of the location of a target corresponding to a signal transmitted from the portable unit, and/or a plurality of target devices at the target location for receiving target signals transmitting by a portable unit and for indicating that a received target signal identifies the respective target.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to guidance systems and in particular tosuch systems using changeable signs to lead a person to a predefinedtarget.

Many human activities involve the need to reach a predefined location orobject. Guidance means for choosing a preferred route or for identifyingthe target location or object are in common use, usually in the form ofsigns. Such signs, clearly visible from a fair distance, allow a personto choose the route to the target without interrupting the travel orrisking travel safety. However, when the number of possible routes ortargets is large, the use of common signs becomes impractical, becausetoo much visual information must be displayed and then read andinterpreted during travel. A changeable sign system capable of providingselectively guidance signals relating to a specific route or target ofan individual, could be highly advantageous in such circumstances.

An example of an existing environment using changeable signs displayingroute and target information is the so-called pick-to-light (PTL) systemfor warehouses. Such commercial systems and their advantages aredescribed in the article “Pick-to-light directs productivity: howeveryou store materials, PTL indicators make for timely and accurateorderpicking” by Schwind, Gene F., Material Handling Engineering, Dec.1993, Page 43, downloaded through Compuserve Information Services. Insuch pick-to-light systems, the pick assignments are stored in a centralcomputer. The central computer communicates with terminals positionednext to stock locations. When a certain pick assignment is activated bythe central computer, lights in the corresponding terminals are turnedon to provide the picker with clear visual guidance signals. Additionalinformation may be generated by the central computer and displayed bythe terminal, such as information relating to the pick quantity. Theterminal may also include input means for keying-in and uploading pickreports. Other prior art references relating to pick-to-light systemsinclude U.S. Pat. Nos. 3,739,339 to Hilihouse et al., 3,908,800 toDrapeau and 4,346,453 to Drapeau et al.

While having many advantages regarding productivity and accuracy, theexisting pick-to-light systems have two major limitations: they canserve only a single picker or a small number of pickers operatingsimultaneously, and they require a costly communication infrastructurebetween the central computer and all terminals.

OBJECT AND BRIEF SUMMARY OF THE INVENTION

The following terms will be used herein as follows:

1. Assignment—a task to be performed including traveling toward andreaching a target location.

2. Operator—a human individual executing an assignment while travelingby foot or by a vehicle.

3. Guidance—the information provided to an operator for aiding inchoosing a preferred route and/or in identifying the target location oritem.

4. Sign—an object positioned next to traffic routes or target locationsfor displaying guidance information viewable by an operator from a fairdistance and usable by operator without interrupting travel. Signs mayincorporate lights and symbols for visibility and clarity.

5. Changeable sign—a sign which changes the information displayedthereon upon receiving an external signal.

6. Central computer—a computer storing assignment information.

The main object of the present invention is to provide a guidance systemusing changeable signs, which system can serve simultaneously a largenumber of operators and does not require a central computer, or acommunication link between a central computer and the signs. Anotherobject of the present invention into provide an assignment reportingsystem operable in conjunction with said guidance system.

According to one aspect of the present invention, there is provided aguidance system for guiding a user to selected targets among a pluralityof targets located within a defined area, comprising:

a portable unit to be carried by the user, including a memory forstoring target information identifying a selected target within saiddefined area, and a transmitter for signals identifying the selectedtarget within said defined area;

and at least one changeable guidance sign at a predetermined locationwithin said defined area, said changeable guidance sign including areceiver for receiving signals transmitted by said portable unit, amemory for storing guidance information relating the locations of saidplurality of targets with respect to said predetermined location of thechangeable guidance sign, a display for displaying the stored guidanceinformation of the location of a target corresponding to as signaltransmitted from said portable unit and received by the changeableguidance sign.

According to another aspect of the present invention, there is provideda guiding system for guiding a user to selected targets among aplurality of targets located within a defined area, comprising:

a portable unit to be carried by the user, including a memory forstoring target information identifying a selected target within saiddefined area, and a transmitter for transmitting signals identifying theselected target within said defined area;

a plurality of target devices, one at each of said target locations,each of said target devices including a receiver for receiving targetsignals transmitted by said portable unit, and a target indicator forindicating that a received target signal identifies the respectivetarget;

and a computer for storing said target data identifying the targetswithin said defined area, and for communicating with said portable unitto download into their respective memories the target informationidentifying selected targets within said defined area.

A number of applications of the invention are described for purposes ofexample, including a warehouse for storing a large number of articles, amuseum having a large number of exhibits, and a parking garage having alarge number of parking spaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a layout of a guidance systemaccording to the present invention.

FIGS. 2A-C are schematic illustrations of the signs in the system ofFIG. 1.

FIG. 3 is a schematic block diagram of a portable unit according to thepresent invention.

FIG. 4 is a schematic block diagram of a changeable traffic signaccording to the present invention.

FIG. 5 is a schematic block diagram of a changeable target signaccording to the present invention.

FIGS. 6A-C are examples of data structures maintained in andcommunicated between various components of the present invention.

FIGS. 7A-C are examples of alternative data structures maintained in andcommunicated between various components of the present invention.

FIG. 8 is a schematic block diagram of a changeable traffic sign with amultiple signal unit.

FIG. 9 is a flowchart describing the operation of the present invention.

FIG. 10 is a schematic illustration of a layout of another variation ofthe guidance system according to the present invention.

FIG. 11 is a flowchart describing the operation of the variation of FIG.10.

FIG. 12 is a schematic illustration of an alternative layout of avariation of the guidance system according to the present invention.

FIG. 13 is a block diagram of a changeable target sign adapted to thevariation of FIG. 12.

FIGS. 14A-D illustrate the data in the assignment memory, guidancetable, guidance signal and assignment table, according to the variationof FIG. 12.

FIG. 15 is a flowchart describing the operation of the variation of FIG.12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made to FIGS. 1 and 2A-C illustrating a layout of apreferred embodiment of the present invention, where the guidance systemof the present invention is used to aid operators in executing pickassignments in a warehouse.

Warehouse 10 accommodates grouped merchandise items (not shown) onshelves 21. Passageways 20 allow access to the merchandise items. Ateach junction formed by the passageways there is provided a changeabletraffic sign 15. A changeable target sign 16 is positioned next to eachgroup of identical merchandise items. The entire area is divided intocells by coordinates 9, to allow coarse location identification bycoordinates such as B5, H11 etc. It would be appreciated that suchcoarse identification of locations can alternatively use room numbers,aisle numbers or other symbols; and the term “coordinates” should beinterpreted hereinafter in its broader sense, as symbols coarselyidentifying localities within the operational area.

An operator, using empty cart 13E and a portable unit 14 attached to thecart, reports at a check-in unit 12. Upon identifying the operator,central computer 11 allocates an assignment for the operator anddownloads it to portable unit 14 through check-in unit 12. Uponreceiving a “Green” light from traffic light 26 of the check-in unit(FIG. 2C), which confirms the successful download of the assignmentinformation, the operator enters the first junction. By communicatingwith the changeable traffic sign 15, the portable unit 14 transmitsthereto traffic information signals, transformed thereon into visibletraffic directions. When arriving to a line of sight with the targetdestination, as identified by the target sign ID transmitted by theportable unit 14, the respective target sign 16 responds with a visiblesignal, identifying the adjacent target location. The operator may usean optional operator interface 32 on portable unit 14 (FIG. 3) to enterassignment report information into the portable unit, such as the extentof the assignment completion. After the assignment completion, theoperator moves to the next traffic sign 15, where he receives directionswhich lead him either to the next assignment, or toward the checkoutunit 17, where portable unit 14 uploads assignment report information,and then the loaded cart 13L has completed its loading assignment.

FIG. 2A illustrates (the appearance of) a changeable traffic sign 15.Infrared receiver (or transceiver, according to the selected embodiment)23 is operative to communicate with portable unit 14. Light arrows 22A,22L and 22R are actuated to guide the operator to move ahead, to theleft or to the right, respectively. Alphanumeric sign 22D displaysinformation identifying the operator or the assignment.

FIG. 2B illustrates a target sign 16. Infrared receiver (or transceiver,according to the selected embodiment) 25 is operative to communicatewith portable unit 14. Light 24L signals to identify the selectedtarget, and alphanumeric display 24D operates to display the operatorsID and assignment information, e.g. the quantity of items to be picked.

FIG. 2C illustrates a terminal unit functioning as a check-in unit 12(or as a checkout unit 17). The terminal unit communicates with portableunit 14 through IR transceiver 27. Red-Green lights 26 provide theoperator with visible indication whether the upload/download ofinformation from/to the portable unit has been completed.

Reference is now made to FIG. 3 which is a block diagram of portableunit 14. Portable unit controller 30 controls the operation of the unit.Operator ID register 34 includes the operators name or code, which ispreloaded during the units initialization, and is used to identify theoperator when uploading or downloading assignment information, and whencommunicating with traffic and target signs to identify the operatorsidentity thereon. Operator interface 32, e.g. a keyboard and LCDdisplay, is used to key-in the operator's ID, to be stored in register34, and assignment report information, to be stored in assignment memory31. Assignment memory 31 contains assignment information downloaded fromcomputer 11 through check-in unit 12, and report information keyed-inthrough operator interface 32.

Infrared transmitter 36 and receiver 38, driven through drivers 35 and37, respectively, are operative to communicate with traffic signs 15,target signs 16, check-in units 12 and check-out units 17. Power supply33 energizes all other parts of the portable unit 14.

FIG. 4 is a block diagram of the changeable traffic sign 15 of FIG. 1.controller 40 controls all the operations of the sign. Guidance table 41includes preloaded information useful for guiding the operator, as willbe described in relation to FIGS. 6B and 7B below. Traffic display 22,driven through driver 43, shows visual guidance signals as described inrelation to FIG. 2A. The visual guidance signals are displayed for apredetermined delay after the actuating signal, received from portableunit 14, ceases. Receiver 44, driven through driver 45, is operative toreceive signals from portable units 14. Transmitter 47 and driver 46 areoptional for transmitting signals to portable units 14, if theembodiment of FIGS. 7A-C is selected. Power supply 42 energizes theother parts of the changeable traffic sign.

FIG. 5 is a block diagram of the changeable target sign 16 of FIG. 1.Controller 50 controls all the operations of the sign. Target IDregister 51 includes preloaded target ID information identifying thetarget, e.g. the code of the adjacent items identified by the sign.Target display 24, driven through driver 53, shows visual signals asdescribed in relation to FIG. 2B. The visual signals are displayed for apredetermined delay after the actuating signal, received from portableunit 14, ceases. Receiver 54, driven through driver 55, is operative toreceive signals from portable units 14. Transmitter 57 and driver 56 areoptional for transmitting signals to portable units 14, if theembodiment of FIGS. 7A-C is selected. Power supply 52 energizes theother parts of the changeable target sign.

FIGS. 6A-C and 7A-C relate to two preferred embodiments of the datadistribution between the portable unit and the changeable signs: Theembodiment of FIGS. 6A-C simplifies the portable unit and allowsreceive-only operation of the changeable traffic signs 15. Theembodiment of FIGS. 7A-C simplifies the data stored in the changeabletraffic signs, but requires more complicated data in the portable unitsas well as receive-transmit capability at the changeable traffic signs15.

FIG. 6A illustrates the data stored in the assignment memory 31 ofportable unit 14 in FIG. 3, according to a first preferred embodiment.Each line describes a separate assignment Each assignment is describedby its target location coordinates (9 of FIG. 1), the ID of the target,corresponding to the content of the respective target ID register 51(FIG. 5), and the assignment details. Memory space is reserved forreport information for each assignment, to be keyed-in, upon assignmentcompletion, through operator interface 32 (FIG. 3). FIG. 6B describesthe contents of the guidance table 41 of FIG. 4 in said first preferredembodiment. Each traffic sign 15 includes a specific, preloaded tablewhich contains directions to each possible coordinate designation. Thus,in the example of FIG. 6B, coordinate A1 (see 9 in FIG. 1) correspondsto the direction “LEFT”, i.e. in order to reach the location Al, theoperator should turn left at this specific sign. Other coordinates inthe table may match directions such as “AHEAD” or “RIGHT” according totheir actual physical location. Obviously, different signs will includedifferent tables, according to their physical location. The table foreach sign can be prepared manually or by using computer assistance. FIG.6C relates to the same first preferred embodiment, describing theguidance signal transmitted continuously by portable unit 14 throughtransmitter 36 (FIG. 3). The guidance signal includes the targetlocation, the target ID and the target details (all from FIG. 6A), andthe operator ID (from register 34 of FIG. 3). When this guidance signalis received by a traffic sign (FIG. 2A) the sign displays the trafficdirection according to the guidance table of FIG. 68B, and also showsthe operator's ID, to avoid ambiguity among neighboring operators. Whenthe signal is received by a target sign (FIG. 2B), the sign examines thesignal's “target ID” contents, and if there is a match, the signprovides an eye-catching, visible signal and displays the operator IDand assignment details.

It would be appreciated that addressing (in FIG. 6A) each target by bothits coordinates and target ID code is just a matter of practicalconsiderations. In an application such as a warehouse, there are twoadvantages to this approach: (a) locations in a warehouse accommodating20,000 items may still be coarsely identified by, say, 100 coordinatesymbols (A1-J10), sufficient for navigation among the changeable trafficsigns, which will reduce the size of and simplify the guidance tableincluded in each traffic sign; (b) items in the warehouse may be movedfrom time to time to different locations; the target sign will then bemoved with the corresponding items, the central computer will be updatedto associate the moved items with their new location coordinates, but nochange will be required in the memories of the traffic and target signs.In other applications, however, where targets are fixed in theirlocation, FIG. 6A may be modified by eliminating the “Target Location”column, in FIG. 6B the “Location” column will be replaced by “Target ID”column for specifying the directions from each sign to each target ID,and in FIG. 6C the “Target Location” data will be eliminated from theguidance signal.

FIG. 7A illustrates the data stored in the assignment memory 31 ofportable unit 14 in FIG. 3, according to a second preferred embodiment.Each line describes a separate assignment. Each assignment is describedby its entire route to the target location, the ID of the target, andthe assignment details. The route is defined by a series of consecutivetraffic signs and the directions preassigned for each such sign; forexample, assignment number I in FIG. 7A reads: “at sign #1 turn left;then, at sign #3 turn right; at sign #6 go straight ahead and at sign #8turn right; then you are expected to hit item #1234 where you pick fourboxes”. Memory space is reserved for report information for eachassignment, to be keyed-in, upon assignment completion, through operatorinterface 32 (FIG. 3). FIG. 7B describes the contents of the guidancetable 41 of FIG. 4 in said second preferred embodiment, which is simplythe sign identification number used in the route directions of FIG. 7A.FIG. 7C relates to the same second preferred embodiment, describing theguidance signal transmitted continuously by portable unit 14 throughtransmitter 36 (FIG. 3). The guidance signal includes the operator ID,and then the next segment of the assignment, which is a pair of either asign # +direction (UR/A), or the target ID +assignment detail, all takenfrom the assignment memory of FIG. 7A. In this case, the portable unit14 communicates with changeable signs (traffic 15 and target 16), toactuate a visual response corresponding to the signal, and then receivesan acknowledge signal from the sign, which causes the messagetransmitted by the portable unit to change to the consecutive messagefrom the assignment memory (FIG. 7A).

The calculation of the contents of the assignment memory, according toeither FIG. 6A or 7A, is preferably made by central computer 11 of FIG.1 and is downloaded to the portable unit 14 through check-in unit 12.The calculation uses mapping information entered manually to associatetarget IDs with physical locations, and in FIG. 7A also route selectionalgorithms, such as those used in many navigation applications, todetermine a preferred route for reaching the target. Alternatively, amanual planning of each assignment can be made by a human attendant, andkeyed-in into central computer 11.

The reliability of the embodiment described in FIGS. 7A-C is stronglydependent upon a flawless operation of the operator and all signs; amalfunction in a single sign, or a single unawareness to a trafficsignal, may break the logical continuity of the route directions, thusleading to unresolvable situations. For this reason, the embodiment ofFIGS. 6A-C is preferable and, unless otherwise specified, will be usedhereinafter.

FIG. 8 describes a preferred embodiment for a changeable traffic sign,for environments where many operators operate simultaneously. In such acase, using the traffic sign of FIGS. 2A and 4 may be insufficient, asseveral operators may approach the same traffic sign simultaneously.This embodiment, adapted as an example to the case of FIGS. 6A-C (notransmission capability is needed in the sign) receives guidance signalsfrom portable units 14 through receiver 44. In this case, thetransmission of guidance signals (FIG. 6C) should preferably occur withrandom intervals, so that if signals from two portable units 14 happento coincide, then the next signals will probably be received withoutinterference. When a proper signal is received by changeable trafficsign 15 of FIG. 8, sign controller 80 assigns it to one of the pluralityof displays 82A . . . 82N; if another signal is received before thefirst one expires, it is displayed on the next available display of 82A. . . 82N, and so on.

FIG. 9 is a flowchart, summarizing the operation of a preferredembodiment of the system according to the present invention; referenceis also made to FIG. 1. In block 90 the operator reports at check-inunit 12, where, in block 91, his assignment list is downloaded to hisportable unit 14 in the form of a guidance table (e.g. FIG. 6A). A greenlight 26 on check-in unit 12 indicates that the download process hasbeen completed, and the operator moves into the warehouse area, facingthe first changeable sign (block 92), which is a traffic sign (blocks93, 94). Traffic sign 15 receives a guidance signal (e.g. FIG. 6C) andresponds with displaying traffic directions, by matching the directioninstruction (from FIG. 6C) with the target location coordinates,according to the guidance table of FIG. 6B. The operator ID included inthe guidance signal, is preferably also displayed by traffic sign 15, toassure the operator that the displayed message relates to him. Thedisplayed traffic direction, e.g. in a form of an illuminated arrow,leads the operator to the next changeable sign (block 92), which iseither a traffic sign or a target sign (block 93). If it is a trafficsign, the procedure described above repeats; if it is a target sign, atblock 95 the sign with the matching target ID responds to the guidancesignal (FIG. 6C) by blinking with an eyecatching fight and displayingthe assignment details, along with the operator ID, taken from theguidance signal of FIG. 6C. The operator then executes the assignment(still in block 95), and, if appropriate, keys-in report informationinto portable unit 14. If the assignment has been the last assignment,as indicated in the contents of the assignment (e.g. “pick 8 boxes andreport at checkout #6”), the operator moves then to a checkout unit 17,where the report information is uploaded from portable unit 14 tocentral computer 11 via checkout unit 17. If the assignment has not beenthe last one in the assignment memory (FIG. 6A), the operator approachesthe next traffic sign and the procedure described above is executed onceagain.

Another preferred embodiment will be described herein relating to aguidance system for museum visitors interested in visiting selectedexhibits. This embodiment is described below in reference to FIGS. 2A,2B, 3, 4, 5, 6A-C 10 and 11.

FIG. 10 describes a museum 100 with halls and passageways 104 enablingvisitors to access and observe exhibits. A target sign 16 is placed nextto each exhibit. Traffic signs 15 are placed at each junction. At eachentrance door 101E there is a basket 102E containing portable units 14,which are hand held units (FIG. 3, with receiver 38 and receiver driver37 eliminated). At each exit door 101X, there is a basket 102X where thevisitors return the portable units 14 upon leaving the museum.

Reference is now made to FIG. 11, describing the operation of the systemof FIG. 10. In block 110 the visitor receives his portable unit 14 atentrance door 101E. In block 111 the visitor uses operator interface 32(FIG. 3) to key-in his ID (e.g. name), and a selected list of exhibits,each identified by its location coordinates and exhibit code, as takenfrom the exhibition catalog or map. This information establishes thecontents of registers 31 and 34 of FIG. 3, according to a simplifiedversion of the table of FIG. 6A, where the “assignment details” and“report” columns are eliminated. Then the visitor moves into the museumarea, facing the first changeable sign (block 112), which is a trafficsign (blocks 113, 114). Traffic sign 15 receives a guidance signal (FIG.6C, with the “Assignment Details” eliminated) and responds withdisplaying traffic directions, by matching the direction instruction(from FIG. 6C) with the target location coordinates, according to theguidance table of FIG. 6B. The visitor ID included in the guidancesignal, is preferably also displayed by traffic sign 15, to assure thevisitor that the displayed message relates to him. The displayed trafficdirection, e.g. in a form of an illuminated arrow, leads the visitor tothe next changeable sign (block 112), which is either a traffic sign ora target sign (block 113). If it is a traffic sign, the proceduredescribed above repeats, if it is a target sign, at block 115 the signwith the matching target ID responds to the guidance signal (FIG. 6C) byblinking with an eye-catching light, along with the visitor ID takenfrom the guidance signal of FIG. 6C. The visitor then observes theexhibit (still in block 95). If the exhibit has been the last one on thelist, as indicated on the display, the visitor moves to an exit door101X, where he returns his portable unit 14 into basket 102X. If theexhibit has not been the last one in the assignment memory (FIG. 6A),the visitor approaches the next traffic sign and the procedure describedabove is executed once again.

Another variation of a warehouse guidance system will be described inreference to FIGS. 12-15, In this variation, there are no specificentrance or exit gates; instead, guidance and/or reporting informationis communicated to and from the portable units throughout the warehousearea via a wireless communication link. This allows frequent, flexiblechanges of the assignments even during their execution.

FIG. 12 illustrates warehouse 120, where central computer 11 is linkedto a plurality of infrared transceivers 127 deployed throughout thewarehouse ceiling to communicate with all changeable target signs 126,changeable traffic signs 15 and portable units 124. Such infraredcommunication rinks are known in the art and operate commercially.Transmission is usually made by broadcasting coded signals, includingaddress information identifying specific units. Each unit which includesan infrared receiver examines the received signal, and takes intoaccount only messages addressed to it, according to the contents ofaddress register 34 (FIG. 3), 48 (FIGS. 4 and 8) or 51 (FIGS. 5 and 13).Uploading information is made by portable units 14 (FIG. 3) by employingtransmitter 36 to communicate with any of the ceiling transceivers 127(FIG. 12).

FIG. 13 describes a preferred embodiment of the changeable target signaccording to the variation of FIG. 12. It is similar to the changeabletarget sign 16 of FIG. 51 except that storage device 131, includingassignment table information (see FIG. 14D), is added.

FIG. 14A describes the contents of the assignment memory register 31 ofportable unit 14 (FIG. 3) according to the variation of FIG. 12. Thecontents is a list of assignments, each identified by a target ID. Thislist can be downloaded or modified by central computer 11, bycommunication between the central computer and a selected portable unitthrough ceiling transceivers 127. The list contains just the target ID,and memory space is reserved for keying-in report information viaoperator interface 32 (FIG. 3). FIG. 14B describes the contents ofguidance table 41 (FIGS. 4 and 8), assigning a direction (“left”,“right”, “ahead”) from each traffic sign 15 to each active target. Thisinformation, relating only to active targets (i.e. targets which areassociated with current assignments), is computed by central computer 11and is downloaded selectively to relevant traffic signs 15, according toa reasonable path of the operator; in one case all traffic signs canreceive guidance signals to all active targets; in another case, to savecommunication time between the central computer and the traffic signs,signs which are remote from the path of the operator may be notcommunicated. FIG. 14C describes the contents of the guidance signaltransmitted continuously by portable unit 14 via transmitter 36. Itincludes the target ID, to be identified and responded to by trafficsigns and the corresponding target sign, and the operator ID to bedisplayed on the responding signs, to avoid ambiguity with directionsaimed at neighboring operators. FIG. 14D describes the contents ofassignment table 131 (FIG. 13), which has been added to this variation.This information is downloaded to the target sign by central computer 11via ceiling transceivers 127 (FIG. 12). When an operator identifieshimself by transmitting the guidance signal (FIG. 14C), the assignmentdetails corresponding to this operator, along with a guidance signal andthe operator's ID, are displayed on the changeable target sign 126.

FIG. 15 summarizes the operation procedure of the variation of FIG. 12.In block 150 the operator awaits near a sign. As no assignment has beendownloaded yet to his portable unit, his portable unit transmits nosignal and hence no response is received. In block 151 central computerhas selected and computed an assignment for the operator, andaccordingly transmits the contents of the assignment memory 31 to theoperators portable unit 14 (FIGS. 3 and 14A), the contents of guidancetable 41 (FIGS. 41 and 14B) to all relevant traffic signs 15, and thecontents of assignment table 131 (FIGS. 13 and 14D) to the selectedtarget sign 126. As a result, portable unit 14 starts transmitting theguidance signal (FIG. 14C). In block 152 the relevant adjacent signresponds to the guidance signal. If it is a traffic sign (block 154) theoperator receives traffic directions and travels accordingly to the nextsign (block 153). If it is a target sign (block 155) the operator visitsthe target, executes his assignment according to the details displayedon the target sign, reports as appropriate, and then, according to thedetails of the assignment, he executes the next assignment (block 152),or completes his task (block 157).

Another application of interest is a parking garage, where an emptyspace is allocated to each car entering an entrance gate. A portableunit, preloaded with the allocated parking spot details, is handed orautomatically dispensed to the driver at an entrance gate. The portableunit interacts with changeable traffic signs to produce drivingdirections, and then the specific, preassigned parking spot is clearlyidentified by its changeable target sign. In this case, thecommunication between the portable unit and the preassigned target signconfirms that the driver has reached his parking space, which ispreferably recorded in the assignment memory (FIG. 6A or 7A) as reportinformation, and reported at an exit gate (where the portable unit isalso returned) for control purpose.

Another variation of interest relates to a warehouse divided into zones,each zone served by an operator. The portable unit is attached to a cartor a box which accommodates the picked items, thus a pick assignment maybe executed by several operators, each moving and loading the cart orbox in his turn. As the cart or box is moved and loaded by a zone'soperator, the attached portable unit communicates with and triggers thechangeable signs in its vicinity in accord to the respective assignment.At the border between two zones, the cart or box, along with theattached portable unit, is left to be moved and loaded by the adjacentzone's operator, and so on, until the assignment is completed.

In still another variation of interest, portable unit 14 (FIG. 3) alsoincludes a display screen controlled by portable units controller 30.When communicating with changeable traffic sign 15 or changeable targetsign 16, at least part of the information to be displayed on thesechangeable signs may be displayed on the portable unit's display,instead of or in addition to being displayed on the sign. This may aidthe operator in reading and distinguishing the information relating tohim, and even allow eliminating the display 22 on changeable trafficsign 4 (which actually converts it to a guidance transponder instead ofa sign,) or eliminating the screen 24D of the changeable target sign 16,while leaving the light 24L on the sign for better identification of thetarget.

While the preferred embodiments described above relate principally towarehouse and museum applications, it would be appreciated that theguidance system of the present invention is useful in many otherapplications.

What is claimed is:
 1. A guidance system for guiding a user to selectedtargets among a plurality of targets located within a defined area,comprising: a portable unit to be carried by the user, including amemory for storing target information identifying a selected targetwithin said defined area, and a transmitter for transmitting signalsidentifying the selected target within said defined area; and at leastone changeable guidance sign at a predetermined location within saiddefined area, said changeable guidance sign including a receiver forreceiving signals transmitted by said portable unit, a memory forstoring guidance information relating the locations of said plurality oftargets with respect to said predetermined location of the changeableguidance sign, and a display for displaying the stored guidanceinformation of the location of a target corresponding to a signaltransmitted from said portable unit and received by the changeableguidance sign.
 2. The system according to claim 1, wherein there are aplurality of said changeable guidance signs each at one of a pluralityof predetermined locations within said defined area.
 3. The systemaccording to claim 1, wherein said portable unit memory storesinformation identifying a plurality of targets to be visited insequence, and said transmitter transmits signals identifying therespective selected target to be visited in the sequence.
 4. The systemaccording to claim 1, wherein said system further comprises a pluralityof target devices, one at each of said target locations, each of saidtarget devices including a receiver for receiving target signalstransmitted by said portable unit, and a target indicator for indicatingthat a received target signal identifies the respective target.
 5. Thesystem according to claim 4, wherein each of said portable units alsotransmits its identification to each of the target devices, and each ofsaid target devices also displays the identification of the respectiveportable unit transmitting a signal received by the target device. 6.The system according to claim 4, wherein each of said target devices isa changeable sign displaying information which changes in response tothe target signal received thereby.
 7. The system according to claim 1,wherein there are a plurality of said portable units, each to be carriedby one of a plurality of users of the guidance is system, and whereineach of said portable units transmits its identification to thechangeable guidance sign, and said changeable guidance sign alsodisplays the identification of the respective portable unit transmittinga signal received by the changeable guidance sign.
 8. The systemaccording to claim 7, wherein said changeable guidance sign displayincludes a plurality of display devices for simultaneously displayingguidance information of the locations of a plurality of targets for aplurality of portable units, and the identification of the respectiveportable unit.
 9. The system according to claim 7, wherein the systemfurther comprises a computer for storing said target data identifyingthe targets within said defined area, and for communicating with saidportable units to download into their respective memories the targetinformation identifying selected targets within said defined area. 10.The system according to claim 9, wherein the system further comprises acheck-in unit linked to said computer for communicating with saidportable units to download into their respective memories the targetinformation identifying the selected targets within said defined area.11. The system according to claim 9, wherein said system furthercomprises wireless communication links enabling said computer tocommunicate with said portable units to download into their respectivememories is-the target information identifying the selected targetswithin said defined area.
 12. The system according to claim 1, whereinsaid defined area is a warehouse for storing a large number of articlesat a plurality of locations, each location representing a targetlocation to which the user carrying a portable unit is to be guided. 13.The system according to claim 1, wherein said defined area is a museumhaving a large number of exhibits at a plurality of locations, eachlocation representing a target location to which the user carrying aportable unit is to be guided.
 14. The system according to 1, whereinsaid defined area is a parking garage having a large number of parkingspaces at a plurality of locations, each location representing a targetlocation to which a user carrying a portable unit is to be guided.
 15. Aguidance system for guiding a user to a selected target among aplurality of targets located within a defined area, comprising: aportable unit to be carried by the user, including a memory for storingtarget information identifying the selected target, and a transmitterfor transmitting a target signal representative of the targetinformation; a target device adjacent to said selected target, includinga receiver for receiving signals transmitting by said portable unit, anda target indicator or indicating that a received signal is said targetsignal representative of said target information identifying saidselected target; a computer for storing said target information; and acheck-in unit linked to said computer for communicating with saidportable unit to download into its memory said target informationidentifying said selected target; and a check-in unit linked to saidcomputer for communicating with said portable units to download into itsmemory said target information identifying said selected target.
 16. Thesystem according to claim 15, wherein said check-in unit downloads intothe memory of said portable unit target information of a plurality ofselected targets within said defined area to which the user carrying theportable unit is to be sequentially guided, and wherein said portableunit include a manual input device to sequentially selected each of saidplurality of selected targets.
 17. The system of claim 15, wherein saidcomputer also stores assignment information specifying a task to beperformed by the user at said selected target, the assignmentinformation is also downloaded into the memory of said portable unitwith the respective target information.
 18. The system according toclaim 17, wherein said assignment information is also displayed on saidportable unit.
 19. The system according to claim 17, wherein saidassignment information is also transmitted by said portable unit and isreceived and displayed by the respective target devices.
 20. The systemaccording to claim 17, wherein each of said portable units includes amanual input device for manually inputting report information relatingto the task specified to be performed by said assignment information.